1. Field of the Invention
The invention generally relates to a data recording and playback systems for monitoring processes or occurrences of events which allows the replay and/or analysis of a time sampled signal.
2. Description of Related Art
Event recording and playback devices used to monitor and record events typically fall into one of two types. VCR and tape recording type devices permit the recording of a video and/or other signal and allows later playback of these signals. Other recording and playback devices utilize a circular storage buffer during recording in which recent data over-writes the older data. For instance, U.S. Pat. No. 6,035,367 to Laws discloses a computer file system having looped file structure for data collection of asynchronous events. Thus, Laws reference describes a system that records to a circular storage buffer. However, the system described in Laws terminates recording when a predetermined event occurs.
Other known devices for event recording and playback maintain a circular storage buffer of recorded signal in the manner described above and respond to an event or a trigger by transferring the contents of the circular storage buffer to an intermediate storage location based on predetermined pre-trigger and post-trigger times. U.S. Pat. No. 6,136,338 to Johnson, et al., U.S. Pat. No. 5,845,240 to Fielder, and U.S. Pat. No. 5,821,990 to Rudt, et al. each describe such event recording and playback systems that utilize a circular storage buffer which either stops recording upon the occurrence of an event, or extracts the data related to the event and stores the data at an intermediate storage location as a plurality of sequential files, each file containing a very small time duration. After the data related to the event is extracted and stored, playback of the recorded data is made possible by retrieving the stored data from the intermediate storage location. However, these technologies do not allow simultaneous recording and playback of these signals.
The recording of data signals using circular storage buffers are also known in consumer electronics products as well. Such known consumer products include devices manufactured by TiVo® and ReplayTV® which are designed to record broadcast video. Such devices have a live TV mode in which they simultaneously record and playback television broadcasts from a circular storage buffer. U.S. Pat. No. 5,701,383 to Russo, et al., and U.S. Pat. No. 5,371,551 to Logan et al. describe such consumer television type systems. In particular, Logan et al. discloses a time delayed digital video system that utilize concurrent recording and playback that is implemented by a subsystem digital memory where semiconductor RAM memory and a disk memory are operated by a microprocessor such that incoming signals are constantly recorded as received while, at the same time, delayed signals are being read from the memory subsystem at a different memory location selected by the microprocessor to provide a user-selected time delay.
However, the technology used in the above described consumer devices do not interface to external events. In other words, these consumer devices are not associated to a triggering event but are merely operated to begin collection of data at a particular time. In addition, such time delaying consumer systems are implemented utilizing proprietary hardware architectures and internal programming. Consequently, the known consumer devices cannot be readily used to monitor external events and to record and playback such monitored events.
Furthermore, such proprietary hardware architectures and internal programming are not readily transferable to event recording and playback devices described above which are typically implemented using a programmable computer such as personal computers, servers, or the like. In particular, it is desirable to provide an event recording and playback system that is flexible enough to be readily adapted for application in different environments and to receive information from a variety of monitoring sensors. For instance, depending on the particular application, variety of sensors such as vision cameras, audio sensors, vibration sensors, thermal sensors, and the like may be used, individually, or in combination. Therefore, a computer based implementation of the event recording and playback devices is desirable since such computers provide the flexibility to be adapted for various applications.
Current computer based video recording and playback systems such as those suggested in the reference Rudt et al. and Fielder have significant limitations and disadvantages in that the event data captured and stored in the intermediate storage location cannot be easily viewed. Each of the plurality of files stored in the intermediate storage must be retrieved and viewed. Alternatively, two or more of the files may be retrieved and combined to provide a more continuous playback of a longer time interval. However, it is often desirable for the user of the event recording and playback device to quickly view or otherwise access the stored data for a segment of time monitored, and to quickly move on to another segment of time monitored. Having to retrieve one or more of the plurality of files that are stored in the intermediate storage location, and/or to compile a plurality of files is cumbersome and time consuming.
Therefore, there exists an unfulfilled need for a data recording and playback system for monitoring processes or occurrences of events which avoids the disadvantages of the prior art. In particular, there exists an unfulfilled need for such a data recording and playback system that allows easy and rapid viewing of the recorded data.